1. Field of the Invention:
The invention relates to an ocean-going ship, and an ocean-going vessel with a stern tube seal arrangement for sealing a stern tube for a propeller drive shaft, and an arrangement for sealing propeller drive shafts in an ocean-going vessel.
2. Background Information
Seal arrangements for ships of this type are known in a multiplicity of embodiments. In actual use it has been shown that during operation by way of axial oscillations of the shaft the associated bushing is moved to and fro. Thus, oscillations of approximately 11 Hertz arise in the case of larger vessels. This causes overpressures and negative pressures in the lubricating oil chamber in relative short time periods, because a pressure equalization by way of the stern tube bearing and the conduits up to the upper tank is substantially not possible.
The overpressure or the negative pressure, respectively, in the lubricating oil chamber affects the seal rings to a large extent. In connection with this there often arises a large loss of oil into the stern tube. The large strain placed on the seals gives frequently rise to operational problems.
It is the object of the present invention, in at least one embodiment, to improve the seal arrangement embodiment of the type described and to minimize in a simple manner oil pressure fluctuations and to avoid functional problems arising because of oil pressure fluctuations.
The invention teaches that this object can be accomplished by an ocean-going ship, said ship comprising: a propeller; a shaft mounted for rotation of said propeller; bearing means to journal said shaft; a bushing mounted on said shaft; said bushing having a first end immersed in water when said ship is afloat on water, and a second end opposite said first end near said bearing means; a plurality of seals mounted on said bushing; said plurality of seals comprising lip seals; a plurality of annular elements to maintain said plurality of seals in spaced apart relationship on said bushing; said plurality of annular elements being configured and disposed to provide a plurality of first annular chambers for lubricant to lubricate at least said bearing means; said bushing comprising an annular surface at said second end thereof; said annular surface at said second end of said bushing being configured and disposed to form a portion of a second annular chamber for lubricant to lubricate said bearing means; said plurality of seals being configured and disposed to minimize ingress of water and to retain lubricant for said bearing means in said second annular chamber; at least one seal of said plurality of seals being configured and disposed adjacent to said bearing means; a sensor; said sensor being configured and disposed to sense at least one parameter representative of pressure variations of a lubricant in said second annular chamber due to axial oscillations of said shaft; said sensor being further configured to produce a signal representative of pressure variations of a lubricant in said second annular chamber due to axial oscillations of said shaft; a comparator element; said comparator element being configured and disposed to receive signals representative of pressure variations of a lubricant in said second annular chamber due to axial oscillations of said shaft; said comparator element further being configured to compare signals representative of pressure variations of a lubricant in said second annular chamber due to axial oscillations of said shaft with desired pressure conditions; a control element; said control element being configured and disposed to receive signals from said comparator element to effectuate compensation for pressure variations of a lubricant in said second annular chamber due to axial oscillations of said propeller shaft; an expandable and contractable element; said expandable and contractable element being configured to be filled with a pressure medium and to exert pressure on a lubricant in said second annular chamber to compensate for pressure variations of a lubricant in said second annular chamber due to axial oscillations of said propeller shaft; said comparator being further configured to pass signals, to said control element, to effectuate compensation for pressure variations of a lubricant in said second annular chamber due to axial oscillations of said propeller shaft; and said control element being configured to control the extent of filling of said expandable and contractable element to thus adjust pressure conditions exerted upon a lubricant in said second annular chamber with a phase shift of approximately 180 degrees for an actual lubrication pressure condition in said second annular chamber; thus forming an arrangement to compensate and to minimize lubrication pressure fluctuations, of a ship""s stern tube seal arrangement, due to Coaxial oscillations of said propeller shaft.
The invention also teaches that the foregoing object can be accomplished in a ship by an arrangement to compensate lubrication pressure fluctuations in a ship""s stern tube seal arrangement due to axial oscillations of a ship""s propeller shaft, said arrangement comprising: a shaft mounted for rotation of a ship""s propeller; bearing means to journal said shaft; a bushing mounted on said shaft; said bushing having a first end immersed in water when the ship is afloat on water, and a second end opposite said first end and adjacent to said bearing means; a seal arrangement configured and disposed to minimize ingress of water and to retain lubricant for said bearing means; a lubricating arrangement configured and disposed to provide lubricant to said seal arrangement and to said bearing means; a sensor; said sensor being configured and disposed to sense at least one parameter representative of pressure variations in said seal arrangement due to axial oscillations of said propeller shaft; said sensor further being configured to generate signals representative of pressure variations in said seal arrangement; a comparator element; said comparator element being configured and disposed to receive signals, representative of pressure variations in said seal arrangement, from said sensor; said comparator element further being configured to compare signals representative of pressure variations in said seal arrangement with desired pressure conditions; a control element configured and disposed to receive signals from said comparator element to effectuate compensation for pressure variations in said seal arrangement due to axial oscillations of said propeller shaft; and an expandable and contractable element; said expandable and contractable element being configured to be filled with a pressure medium and to exert pressure on a lubricant in said lubricating arrangement to compensate for pressure variations in said seal arrangement due to axial oscillations of said propeller shaft; said comparator being further configured to pass signals, to said control element, to effectuate compensation for pressure variations in said seal arrangement due to axial oscillations of said propeller shaft; and said control element being configured to control the extent of filling of said expandable and contractable element to thus adjust pressure conditions exerted in said lubricating arrangement with a phase shift of approximately 180 degrees for the sensed lubrication pressure in said lubricating arrangement; thus forming an arrangement to compensate and to minimize lubrication pressure fluctuations, of a ship""s stern tube seal arrangement, due to axial oscillations of said propeller shaft.
The invention further teaches that the foregoing object can be accomplished by an arrangement to compensate lubrication pressure oscillations in a ship""s stern tube seal arrangement due to axial oscillations of a ship""s propeller shaft, said compensating arrangement comprising: a sensor configured to be disposed to sense at least one parameter representative of pressure oscillations, in a ships""s stern tube seal arrangement, due to axial oscillations of a ship""s propeller shaft; and an arrangement configured to be disposed to compensate for oscillations of lubrication pressure due to axial oscillations of a ship""s propeller shaft to compensate for and to minimize stern tube seal lubrication pressure oscillations of a ship""s stern tube seal arrangement due to axial oscillations of a ship""s propeller shaft; said compensation arrangement being configured to receive a signal from said sensor, to thus form an arrangement to compensate for and to minimize lubrication pressure oscillations in a ship""s stern tube seal arrangement due to axial oscillations of a ship""s propeller shaft.
The invention teaches, in one embodiment, that pressure fluctuations that arise in the lubricating oil chamber are passed in the form of axial oscillations of the shaft via an annular piston surface of the bushing, by way of a sensor, for the determination of pressure changesxe2x80x94as actualxe2x80x94value to a comparator element, which comparator element actuates a control element, such as, a pressure valve, in order to control the extent of filling of an annular tubular expandable body, whereby the expandable body impacts on the lubricating oil chamber and impacts the volume of the lubricating oil chamber with a phase shift of approximately 180 degrees in reference to the sensed pressure impulse, so as to attain a minimized pressure fluctuation in the lubricating oil chamber.
Thus, there is carried out a countervailing control, by way of the expandable body, for compensation of oil pressure fluctuations configured by sinusoidal oscillation. The expandable body always then attains a maximum or minimum when the oil pressure in the lubricating oil chamber has attained a minimum or a maximum. The oil that is displaced from the surface of the annular piston is accordingly absorbed by the condition of the expandable body.
An advantageous embodiment resides therein that the sensor is disposed in the lubricating oil chamber and/or the axial oscillation of the shaft can be passed by way of a measuring flange with associated measuring sensor, for the formulation of an actual value, to the compensating element.
It is also advantageous that the expandable body is disposed in an annular chamber ahead of a seal which is disposed alongside the shaft bearing and ahead of the lubricating oil chamber and the expandable body is connected to the lubricating oil chamber by way of an oil channel.
It is also provided that the expandable body is configured to be impacted on one side and acts horizontally or vertically upon the lubricating oil chamber.
As an alternative an expandable body is configured with a receiving space for retention of lubricating oil and with its closed, facing-away side can be impacted on three sides in a controllable chamber as controllable pressure chamber.
For the purpose of further improvement and optimization it is suggested that the comparator element is configured as controller which is supplied with a guide value, and the controller and control element are part of a control circuit.
The above-discussed embodiments of the present invention will be described further herein below with reference to the accompanying figures. When the word xe2x80x9cinventionxe2x80x9d is used in this specification, the word xe2x80x9cinventionxe2x80x9d includes xe2x80x9cinventionsxe2x80x9d, that is, the plural of xe2x80x9cinventionxe2x80x9d. By stating xe2x80x9cinventionxe2x80x9d, the Applicant does not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicant hereby asserts that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.